Current intraocular lenses (IOLs) are often inserted into the eye through a small scleral tunnel incision. As is appreciated by those skilled in the art, successful implantation of the IOL requires it to have sufficient structural integrity and elasticity, and a sufficiently small size to permit deformation and insertion through the incision. Some representative IOLs and surgical procedures are described by Doyle et al U.S. Pat. No. 5,423,929 and Brady et al U.S. Pat. No. 5,476,513, the disclosure of each of which is incorporated herein in its entirety by reference.
Silicone polymers mechanically reinforced with a silica material have been developed as an optical material for IOLs. The small size requirement for the lens makes it advantageous that it also has a high refractive index. Accordingly, the silicone polymer of the IOL preferably is selected to have a high refractive index, generally of 1.42 and above. Inasmuch as such silicone polymers alone often lack adequate mechanical strength, a silica reinforcer, for example, fumed silica particles, is often finely distributed in the silicone polymer. Exemplary reinforced silicone elastomers for use in these IOLs have been described by Christ et al U.S. Pat. Nos. 5,376,694; 5,494,946; and 5,661,195, the disclosure of each of which is incorporated in its entirety herein by reference. A particularly preferred crosslinkable silicone copolymer of these previous IOLs is a polydimethyldiphenylsiloxane having the following formula:

Previous IOLs, however, suffer from a tendency of the silicone copolymer to “crystallize” whenever the mol % of diphenyl in the molecule is increased in an effort to raise its refractive index. Such crystallization, which is believed to be due to the close packing and alignment of phenyl rings in the molecule, causes the optical properties of the IOLs to be compromised.
In an effort to prevent or reduce crystallization, Yang et al U.S. Pat. No. 5,512,609 have proposed raising the refractive index of the crosslinked silicone polymer to at least 1.50 by inserting a spacer group between the aryl group and the silicon atom, thereby permitting increased flexibility in the molecule. In this approach, a polymeric resin component preferably is employed to reinforce the lens body, with the polymeric resin component being selected so that its index of refraction is substantially matched to that of the silicone copolymer.
There continues to be a need to provide novel IOLs having high refractive indexes, preferably above about 1.46. Such IOLs should permit reduced thicknesses and smaller incisions while retaining good optical and mechanical properties.